I recently posted a question that quite promptly got a number of decent answers. One of those answers led me to a closely related but slightly different question. What's the best way to bring up that additional question? I could..

ask the new question in an "answer" to my original question (this is what I did, but it's kind of colder and, I suspect, less likely to be seen by people),

It's disrespectful to those who answered your original question because you risk their answers getting downvoted now that their answers don't sync with the question. There isn't a limit of questions that I'm aware of, but multiple questions is also good for you because you'd get +2 rep for every question answered.

The idea of stackoverflow is to be a wiki of ideas, so if it's close to your original question, go ahead and edit the question. Someone with enough reputation can add the answer to that part to the best answer.